Cat 6 & counting ...

Dorian deserves to be a Cat 6 hurricane,
the first of many to come as civilization moves further into the Anthropocene.

Category 5 Atlantic hurricanes are rare. Only 7% of the 243 hurricanes observed since accurate satellite measurements began in 1983 have reached that catastrophic intensity. And it is truly exceptional to see a category 5 hurricane as strong as Hurricane Dorian, which powered ashore on Great Abaco Island in The Bahamas on September 1, 2019, with sustained winds of 185 mph and gusts up to 220 mph. Winds of this strength would make Dorian worthy of a category 6 rating, if it existed. (For those of you unfamiliar with me, know that there is already a Category 6—it’s the name of a blog I co-author with Bob Henson over at Weather Underground, specializing in daily updates of global tropical cyclone activity).

The Saffir-Simpson Hurricane Wind Scale, which is used to rank hurricane winds on a scale of one to five, stops at category 5: sustained 1-minute average wind speeds of at least 157 mph (70 m/s). If we were to add a category 6 to the scale, we must consider that the scale is not quite linear. Winds for a category 2 hurricane span a range of just 15 mph, for example, but winds for a category 4 storm span a range of 27 mph. Regardless of this non-linearity, a one-category increase in intensity on the scale results in approximately four times more wind damage, according to the National Hurricane Center.

Cat 6 candidates to date ...

If one uses 185-mph winds as the threshold for category 6, only five Atlantic hurricanes in recorded history would qualify. If we lower the threshold to 180 mph, there are a total of eight that would rate as a category 6:

• 190 mph: Allen 1980
• 185 mph: Dorian 2019, Labor Day 1935, Gilbert 1988, Wilma 2005
• 180 mph: Mitch 1998, Rita 2005, Irma 2017

It's just a matter of time.